In recent years, small tractors, riding lawn mowers and similar vehicles, having a power capacity in the order of roughly 5 to 25 hp have been widely sold for such purposes as the cutting of lawns, tilling the soil, plowing snow, hauling and other tasks around the home or farm. Like all mechanical equipment, these vehicles require servicing such as the removal of rotary blades for sharpening or replacement, periodic lubrication and/or oil changes, etc. It is oft times inconvenient and always expensive to have such maintenance performed at a central service facility having the necessary lifts to elevate the vehicle bodily for performing these operations since the vehicle must be loaded onto some type of carrier and transported to that facility, and delays in the completion of such servicing are common. Many of these servicing operations are of the type that can be performed by the average owner and indeed many owners would prefer to do this work themselves in order to save time and money and, moreover, insure themselves of satisfactory execution.
However, many maintenance procedures require that at least one end of the tractor be elevated at least about one foot and often somewhat higher above the ground so that the operator can have access to the undercarriage of the vehicle where the mower blade is often situated or the lubrication fittings located. Despite their relatively small size and capacity, these vehicles nevertheless have a considerable weight which typically exceeds the lifting strength of the average person. Of course, conventional jacks of the type used for jacking automobiles and the like could be employed, but as is well known by those familiar with automotive mechanics, these jacks are not sufficiently stable in operation to permit work to be safely performed beneath the vehicle suspended therefrom but must be used together with jack stands; but since each side of an end of the tractor must be jacked separately and then placed on a separate jack stand for stable elevation, this is inconvenient and time consuming.
Various kinds of portable jacks have been suggested for various purposes, such as those disclosed in U.S. Pat. Nos. 1,377,147; 1,949,718; 1,949,719; 1,956,797; 2,789,706; 2,814,394; 3,091,431; 3,195,860 and 4,180,252, but none of these are well suited for the function described above.